1. Field of the Invention
The present invention relates in general to a tamper-evident closure system for sealing a container. More particularly, the present invention relates to a an improved neck finish and a closure with a reinforced tear tab.
2. Description of the Related Art
Many tamper-evident closure structures available in the prior art have a removable portion or lower skirt frangibly attached to the upper skirt of the cap. The removable portion typically includes a locking structure, such as ratchet teeth or beads, which cooperate with the locking structure on the neck to prevent removal of the closure so long as the removable portion is intact. A tear tab depending from the lower skirt may be gripped by a user to separate the removable portion from the remainder of the cap when opening the container. The removable portion may be formed with a vertical line of weakness adjacent the tear tab to facilitate opening of the container. A vertical rib may be formed on the back surface of the tab to ensure that the removable portion ruptures along the vertical line of weakness when a user grips the tab and pulls it away from the container neck.
Another type of closure, shown for example in U.S. Pat. Nos. 5,224,616 and 5,284,265, generally includes a top, a skirt depending from and frangibly joined to the top, and a tab joined to the skirt to facilitate removal of the skirt from the top. The interior of the skirt includes a retainer such as a rib or bead which engages a retainer formed on the exterior of the neck to retain the closure on the neck.
Depending upon the material used to manufacture the cap, the tear tab may be quite flexible. During shipment and storage of the cap, the standard tear tab may tend to bend under the weight of the cap and, after a period of time, may become set in the bent position. The deformed tab may interfere with the capping process and require that the cap be discarded. In some capping processes, the tear tab may be used to orient the cap relative to the neck. As the cap travels down a chute, the tab extends into a gap between parallel rails to position the cap so that it is discharged from the chute in a pre-determined orientation. A tab which has been bent inwardly may fail to engage the parallel rails of the chute, with the cap then having any orientation on discharge from the chute. As a result, many of the advantages of providing the cap with a predetermined orientation may be lost. Also, inward or outward bending of the tabs may cause difficulties in properly conveying the closures during the capping process.
A cap having a tab with sufficient rigidity to retain its original shape would avoid these problems occasionally encountered during capping processes. Moreover, a reinforced tab would assist the user in removing the lower skirt from the cap when opening the container. Many types of closures, including for example snap-on, snap-off structures and snap-on, screw-off structures, would benefit from the use of a reinforced tab.
The snap-on, screw-off structures available in the prior art are of two general types--those having thread engagement as initially applied, and those without initial thread engagement. Systems having partial to fill thread engagement on initial application have several advantages over the no-thread system, including the ability to effectively use a liner to seal the neck of the container. The height of the cap and the inner plug, if used, may be reduced. Consumer confusion is also eliminated, since the cap is initially removed from the container by twisting. However, the initial thread engagement systems do not offer the manufacturing and application advantages available with the no-thread system. With some systems, the capping machinery used to apply the closure must twist the closure relative to the container at some point during the application process in order to seat the cap on the neck. An example of such a closure is shown in U.S. Pat. No. 4,625,875 to Carr. Achieving full thread engagement without the use of complicated machinery to twist the cap relative to the neck is preferred.
One modification of this invention provides a snap-on, screw-off system with initial thread engagement by reason of a unique thread design, a unique tamper-evident band and optional means for orienting the closure and container threads to achieve registration prior to straight axial application. The neck is constructed to cooperate with either the standard or reinforced tear tab of a closure to ensure that the cap is aligned with the neck for full thread engagement. The neck construction offers the additional advantage of enabling a consumer to easily grip the tab and open the container. The present invention offers considerable advantages over prior structures as is evident from the description of the related art and the following description of the invention.